U.S. military commanders overseeing food and water distribution in Haiti acknowledged Thursday that the effort remains uneven and that there are places they still have not been able to reach. Food prices on the open market are surging, causing tempers to flare.

Armed food convoys carrying free water and food staples are now a regular sight in the Haitian capital. Each day, U.N. and U.S. troops escort delivery trucks to impromptu distribution points, where the hungry line-up.

In the Bel Air neighborhood, Argentinean U.N. forces oversaw an orderly distribution of hundreds of 20-liter jugs of drinking water. Other distribution efforts have not gone as smoothly. In some instances, they have turned violent.

U.S. Air Force General Douglas Fraser told reporters in Miami that the aid effort is falling short. "We are still not up to meeting the needs of the Haitian people as far as the amount of supplies that are there. There have been some isolated instances where we have been out to distribute aid to citizens, and there has not been enough food. We have not anticipated the demand at each site," he said.

Fraser said that despite the extensive earthquake damage, the country's commercial food networks have restarted and that fresh fruit is available on the streets in Port-au-Prince. But the cost of that food has skyrocketed, angering vendors and their customers.

Two women selling cooking oil, cornmeal, rice and pasta at a retail market in northern Port-au-Prince say wholesalers have raised prices by at least 50 percent and that many of their regular customers cannot afford to buy food.

This vendor says wholesalers are charging more for everything because they say they do not know when they will be able to restock their inventories.

But vendors say one of the biggest reasons for the disrupted food supply is the loss of the biggest wholesale market in downtown Port-au-Prince.

What was just a few weeks ago one of the busiest and most densely populated areas of the city is now largely a wasteland. There are no wholesale vendors on the streets. The covered markets where fresh food used to be sold have collapsed, with scores of people still buried beneath.

Groups of people pick through huge piles of rubble. A young man sorting through the wreckage says there are still useful items buried here and that the survivors can use them.

The man, named Stefan, says he knows that foreigners have sent a lot of aid to Haiti, but that none of it has arrived here. "So we have to survive however we can," he says.

Stefan says he wants to emphasize that this is not stealing. He adds that it is merely the survivors trying to live off of the ruins of Port-au-Prince.